Agonist-induced electrical noise is measured in excitable cells grown in tissue culture. The initial studies of acetylcholine and carbachol induced noise in skeletal muscle cells characterized the postsynaptic ionic channels. A collaborative experiment is in progress to measure glutamate and GABA induced fluctuations in tissue cultured CNS neurons. Theoretical studies of stochastic models of the gating process are directed towards understanding the conformation changes in membrane proteins underlying nerve excitation (channel) activation). A theoretical study was also made to determine the measurable characteristics of transport fluctuations for various models of membrane pore permeation. BIBLIOGRAPHIC REFERENCES: Sachs, F. and Lecar, H.: Acetylcholine-induced current fluctuations in tissue-cultured muscle cells under voltage clamp. Biophys. J. 17: 129-143, 1977. Lecar, H: Physical Mechanisms of Nerve Excitability. In studies in the Natural Sciences, Vol 13: 369-398, 1977, Plenum, in press.